For containers in which the neck (and thread position) must be situated in a specific position relative to the blown bottle shape, there are currently numerous mechanical and optical solutions, which have specific markings, such as an indentation or notch, on the parison (neck). An orientation of the parison or preform is necessary, especial for containers which are manufactured by the “preferential heating” process, in order that the desired temperature profile can be purposely applied on the parison body by means of a heat device, such as, for example, an infrared radiation source, a microwave, a laser, contact heat or the like.
In the mechanical solutions group, a wedge or the like is used for insertion in a notch (indentation, of the preform), thereby fixing this notch and the entire preform. The preform is thereby oriented before tempering the desired profile on to the preform, and with the parison correctly oriented, after screwing on, the closure is situated in the required position. With this solution, therefore, a marking in the form of an indentation, a notch or the like is always necessary on the parison.
With the optical solution, the notch is detected by means of a camera, photoelectric sensor or laser scanner and the preform is oriented by a stepping motor before the required temperature profile can be applied to the preform.
Both with the mechanical solution and with the optical solution, the change of type or change of mouth piece first and foremost involves an additional outlay. Sensors must be provided, which have to be adjusted and set up very precisely in relation to the mouth piece of the parison. This leads to a high, recurrent outlay. Although in the case of a camera system, that is to say in that of the aforementioned optical solution, a lower outlay is to be anticipated, since the necks and markings in the system are known, once the system has been used, there are, however, also limits to such a system. For example, a notch in the support ring can be detected only from below and an indentation on top of the support ring can be detected only from above. The camera would have to be swivelled, or two elements, i.e. two cameras, would have to be used, which carries with it additional costs.
Moreover the camera exposures take place on a reduction starwheel, thereby resulting in additional sources of error due to the transfers. In all the variants hitherto described, that is to say mechanical and optical detection, markings in the form of at least one recess or elevation are formed on the parison, which therefore call for special preforms, which are significantly more expensive to manufacture or procure than standard preforms.
The object of the present invention, therefore, is to create a simple, reliable and significantly more advantageous device, and a significantly more advantageous method, which serve for performing thread position detection of adequate quality.